HR 1099

HR 1099
Chart showing the position of the stars in the constellation Taurus
Location of HR 1099 (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Taurus
A
Right ascension 03h 36m 47.291s[1]
Declination 00° 35′ 15.94″[1]
Apparent magnitude (V) 5.91[2]
B
Right ascension 03h 36m 46.844s[3]
Declination 00° 35′ 15.93″[3]
Apparent magnitude (V) 8.79[2]
Characteristics
Spectral type K2:Vnk[4] (K1 IV + G5 V + K3 V)[5]
Variable type RS CVn[6]
Astrometry
A
Radial velocity (Rv)−21.24±6.62[1] km/s
Proper motion (μ) RA: −32.894 mas/yr[1]
Dec.: −161.772 mas/yr[1]
Parallax (π)33.7528 ± 0.0866 mas[1]
Distance96.6 ± 0.2 ly
(29.63 ± 0.08 pc)
Absolute magnitude (MV)3.6[2]
B
Radial velocity (Rv)−15.34±0.18[3] km/s
Proper motion (μ) RA: −34.359 mas/yr[3]
Dec.: −138.137 mas/yr[3]
Parallax (π)33.8664 ± 0.0226 mas[3]
Distance96.31 ± 0.06 ly
(29.53 ± 0.02 pc)
Absolute magnitude (MV)6.5[2]
Orbit[7]
Period (P)2.83774 d
Semi-major axis (a)10.3 R☉[8]
Eccentricity (e)0.00 (assumed)
Inclination (i)38[9]°
Periastron epoch (T)2,442,767.4 HJD
Argument of periastron (ω)
(secondary)		0.00 (assumed)°
Semi-amplitude (K1)
(primary)		52.6 km/s
Semi-amplitude (K2)
(secondary)		64.1 km/s
Details
Component Aa
Mass1.0[8] M☉
Radius3.7[8] R☉
Surface gravity (log g)3.30[5] cgs
Temperature4,750[5] K
Metallicity [Fe/H]−0.16[10] dex
Rotational velocity (v sin i)39[9] km/s
Component Ab
Mass0.8[8] M☉
Radius1.1[8] R☉
Surface gravity (log g)4.26[5] cgs
Temperature5,500[5] K
Component B
Mass0.78[11] M☉
Radius0.78[11] R☉
Luminosity0.30[11] L☉
Surface gravity (log g)4.55[11] cgs
Temperature4,829[11] K
Metallicity [Fe/H]+0.10[10] dex
Rotational velocity (v sin i)4.1[12] km/s
Age2.2[3] Gyr
Other designations
STF 422, V711 Tau, BD+00°616, GC 4311, HD 22468, HIP 16846, HR 1099, SAO 111291, PPM 146726, ADS 2644, WDS J03368+0035[13][14]
Database references
SIMBADdata

HR 1099 is a triple star system in the equatorial constellation of Taurus, positioned 11′ to the north of the star 10 Tauri.[15] This system has the variable star designation V711 Tauri, while HR 1099 is the star's identifier from the Bright Star Catalogue. It ranges in brightness from a combined apparent visual magnitude of 5.71 down to 5.94,[6] which is bright enough to be dimly visible to the naked eye. The distance to this system is 96.6 light years based on parallax measurements,[1] but it is drifting closer with a radial velocity of about −15 km/s.

This system was discovered to be a double star by F. G. W. Struve in 1822, with the components A and B having an angular separation of 5.4″. (The separation was measured at 6.7″ in 2016.)[16] R. E. Wilson in 1953 determined that the brighter member of this pair, component A, has a variable radial velocity. In 1963, O. C. Wilson noted that the same component shows very high emission cores in the calcium H and K absorption lines.[17] Follow-up observations by O. C. Wilson in 1964 showed that the hydrogen–α line of component A is fully in emission and it displays moderate broadening due to rotation. He found a stellar classification of K3 V for component B, matching an ordinary K-type main-sequence star.[18]

A light curve for V711 Tauri, plotted from TESS data[19]

Observations during 1974–1975 demonstrated that component A is a spectroscopic binary star system of the RS Canum Venaticorum variable class. Given its average magnitude of around 5.9, it is one of the brighter known variables of this type.[20] No eclipses were observed, but an orbital period of 2.838 days was determined. Most of the emission was found to be coming from the more massive member of this pair.[21] Radio emission from the binary was detected by F. N. Owen in 1976.[22] It was shown to be a soft X-ray source in 1978 using the HEAO 1 satellite.[23]

This double-lined spectroscopic binary system consists of an evolving K-type subgiant and an ordinary G-type main sequence star. The two stars are orbiting so close to each other that their tidal effects are giving them an elliptical shape. The subgiant is filling about 80% of its Roche lobe.[5] The chromosphere of the subgiant is one of the most active known, with a deep convective zone powering the magnetic dynamo.[24][4] The G-type companion has a shallow convection zone and is less active.[5]

In 1980, significant variations were found in some spectral features related to surface temperature, suggesting the presence of starspots.[25] Doppler imaging confirmed these starspots are associated with the K subgiant. (It was the first cool star to have its surface Doppler imaged.[26]) The evidence suggests that the spots first appear at low latitude then migrated toward the poles.[20] These spots are much larger than they are on the Sun.[5] About 70% of all spots have been observed at latitudes higher than 50°, particularly around the polar region.[9][24] A polar spot has persisted for at least twenty years.[5]

The baseline apparent magnitudes of the two stars, after subtracting the effects of starspots, is 5.80 and 7.20.[5] Long term monitoring indicates the subgiant has two activity cycles, similar to the 11-year solar cycle. A 5.3±0.1 year cycle is associated with symmetrical flip-flopping of the spotted area between hemispheres. The longer 15–16 year cycle is a periodic variation in the total spot area. The global magnetic field of the star may be precessing with respect to the axis of rotation.[26]

  1. ^ a b c d e f Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference freund2018 was invoked but never defined (see the help page).
  3. ^ a b c d e f Cite error: The named reference GaiaDR3B was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Gray_et_al_2006 was invoked but never defined (see the help page).
  5. ^ a b c d e f g h i j Cite error: The named reference Lanza_et_al_2006 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Strassmeier_Bartus_2000 was invoked but never defined (see the help page).
  8. ^ a b c d e Cite error: The named reference Donati_1999 was invoked but never defined (see the help page).
  9. ^ a b c Cite error: The named reference Donati_et_al_2003 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference pastel was invoked but never defined (see the help page).
  11. ^ a b c d e Cite error: The named reference ticv8 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Earle2017 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference SIMBAD_A was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference SIMBAD_B was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Sinnott1997 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Mason_et_al_2001 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Wilson_1963 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Wilson_1964 was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference MAST was invoked but never defined (see the help page).
  20. ^ a b Cite error: The named reference Vogy_Penrod_1983 was invoked but never defined (see the help page).
  21. ^ Cite error: The named reference Bopp_Fekel_1976 was invoked but never defined (see the help page).
  22. ^ Cite error: The named reference Owen_1976 was invoked but never defined (see the help page).
  23. ^ Cite error: The named reference Walter_et_al_1978 was invoked but never defined (see the help page).
  24. ^ a b Cite error: The named reference Petit_et_al_2004 was invoked but never defined (see the help page).
  25. ^ Cite error: The named reference Ramsey_Nations_1980 was invoked but never defined (see the help page).
  26. ^ a b Cite error: The named reference Berdyugina_Henry_2007 was invoked but never defined (see the help page).